In recent years agricultural vehicles such as tractors and combines have been equipped with automated guidance controls such as Global Positioning System (GPS). The automated guidance controls provide precise operation and control of the vehicles through open fields and similar terrain. Such satellite guidance systems are used in conjunction with on-board computers, drive by wire components, and electro-hydraulic controls to automatically guide tractors in straight lines or predetermined routes with specified overlap between sequential parallel passes on a field, even at night or with poor visibility. Guidance systems are now available that can control the positioning of subsequent passes to within two centimeters.
In some instances GPS may be used not only as a guidance system for the parallel runs down a field, but also as an information source to control the actions at the end of the field. Using a high-precision Real Time Kinematic (RTK) GPS that includes a local portable base station, the GPS can locate the tractor to within less than two centimeters of a desired path. With this capability and the tractor location information transmitted to a computer that records it, the apparatus of the invention knows and can record precisely the tractor's present location and everywhere the tractor has been. It should be noted that the end of field functions operate just as well with the less accurate differential global positioning systems (DGPS).
When using, e.g., a towed mower, while the first circumferential cut is being made around the edges of the field, the computer is mapping the exact location of the boundaries of the field. Furthermore, with the mower dimensions already entered into the computer and sensors on the tractor and the towed mower to provide information to the computer on the position, operation mode, and orientation of the mower, the computer records the dimensions of the portions of the field that have already been cut. Of course, this also provides the computer with the information needed to determine the exact area and location of the uncut portion of the field enclosed within that first circumferential cut. The same control apparatus is useable with other farm implements that independently shift from one side to the other side of the tractor.
When a tractor is equipped with the integrated guidance system of the invention, after the completion of the first circumferential cut around the edges of the field, the computer has sufficient information in its memory to assume automatic steering control of the tractor. The computer steers the tractor along the uncut crop and keeps the tractor's mower full. When the tractor reaches the end of the field, the computer controls the tractor and the mower towed by the tractor, to lift and swing the mower to the opposite side of the tractor to align the mower for the next pass. The computer monitors velocity, transmission setting, steering, and orientation of the towed mower by means of sensors associated with each function, and the recorded information provided by the GPS gives the computer all the information needed on the size and shape of the field and what portion of the crop is uncut. The tractor's control module then uses the information to control conventional electro-hydraulic valves for control of the main functions of the tractor and the towed implement. On the other hand, the operator can also maintain any portion of the control desired.
In some cases, movement of two vehicles must be coordinated, such as, for example, a tractor traveling adjacent to a combine to load the output of a combine while the combine is harvesting a crop. Such movements must be coordinated accurately and precisely so as to avoid collisions of the vehicles. The control system of each vehicle needs to determine the position of the other vehicle so that they can accurately follow one another along a predetermined course. It is known that wireless communication that is used for transmitting position information, has a latency time, i.e., a delay for exchanging information, and that a service interruption in the wireless communication link prevents the exchange of the position data between the vehicle controllers. Such latency and communication interruptions may potentially cause loss of control of the vehicles and the dangers associated therewith.
What is needed, therefore, is a means for automatically controlling movement of coordinated vehicles when there is an interruption to or loss of communication through the wireless communication system that ensures safe stopping trajectories or paths. These and other advantages are provided by the control method described herein.